Learn More About Radiation
Radiation is an unseen particle or wave that is all around us. In nature, radiation is naturally abundant in the land we live on, the atmosphere we breathe, and in space that surrounds our planet. Radiation and the way it interacts, is aiding in our lives everyday. Whether advancing our understanding of our species, saving of lives through health care treatment and diagnosis, providing power with zero greenhouse gas emissions, providing measurements for security, allowing common perishable foods to last longer, or alerting you to a fire in your house, radiation is a critical component of their success.
Radiation interacts in humans mostly through interactions in the DNA. These interactions have the capability to slow down the replication of a cell, alter a cells ability to stop over replicating (cancer), or kill a cell. While many commonly used/surrounding items can alter the DNA in a similar way (chemicals, etc.) a focus of this office is to manage those interactions caused by ionizing radiation. To quantify the amount of radiation that has interacted in humans, science has termed a unit of measurement called dose, with the units of rem (SI unit being Sieverts). While dose comes in many variations, the primary monitor is Total Effective Dose Equivalent (TEDE) of which we can refer to as "dose" for the remainder of this discussion.
Everything is naturally radioactive, the food we eat, the people we sit next to or live with, the houses we live in, the land we walk on, the water we swim in and the air we breath.
- Radon and other natural nuclides we eat, breath or drink deliver on average a dose of 257mrem (2.57mSv) annually.
- Radiation strewn around in space primarily from our sun, known as cosmic radiation, and atmospheric radiation, known as cosmogenic radiation make it to us on earth after mostly being stopped by our earths upper atmosphere and magnetic fields. Cosmic and Cosmogenic radiation on average delivers a dose of 33mrem (0.33mSv) annually.
- Radiation from soil, rocks, and building materials, known as terrestrial radiation on average delivers a dose of 21 mrem (0.21mSv) annually.
- Radiation in diagnostic medical procedures are valuable at looking within the human body to see broken bones such as x-ray's (about 10mrem/scan) or higher definition Computed-Tomography (about 1000mrem/scan). Useful cancer functional imaging such as Positron Emission Tomography (PET) to identify where cancer (readily absorbing sugar), will absorb the radioactive sugar to create an image (about 3600mrem/scan).
- Radiation in therapeutic medical procedures are the application of external beams (Linear Accelerators, Gamma Radiosurgery, etc.) and internal sources (Brachytherapy) to deliver localized cancer specific doses to kill cancerous cells.
- Flying on a plane, at a higher altitude puts one closer to the cosmic radiation source thus a flight from Los Angeles to Paris would be 10mrem (round trip).
Our cells are constantly repairing themselves through checkpoints within cellular replication and other methods to ensure the dividing cell is suitable to divide. Damages to cells occur from environmental toxins, changes in temperature, cell content and radiation. Since our bodies are able to repair from all these damages, estimating risk from radiation (independent of all other common factors) is harder to asses at lower levels. As radiation safety experts, referred to as health physicists, we use data obtained over the years through studies where very high doses are received (some over short periods of time) to relate down to low doses (over prolonged periods of exposure).
For example using the Biological Effects of Ionizing Radiation (BEIR) reports, we can see radiation observable effects at radiation doses above 50,000mrad (similar to mrem). These data points are used to extrapolate down to zero on a risk vs dose plot. We choose the most conservative model, known as the Linear-No-Threshold (LNT) model, that assumes any amount of radiation exposure has an incremental risk. Using this extrapolation, as a worst case scenario is how the radiation safety community has operated and how regulators have created limits. For example a radiation worker is allowed to receive no more than 5000mrem/year whole body dose (U.S. Nuclear Regulation Commission). If one were to assume a risk of 5000mrem using the LNT model, as a radiation worker, the risk of a radiation induced cancer from that dose would be 0.2% (related from the extrapolated 0.04%/rem). This risk estimate is used to illustrate the relatively low risk of radiation exposure. While there is a risk, we manage this risk by an understood phrase known as As Low As Reasonably Achievable (ALARA) where we incorporate minimizing radiation dose through:
- Decreasing time spent around a source,
- Increase distance from the source, and
- Implementing appropriate shielding around the source.
While using radiation may pose risks, when those risks are understood and properly managed, we can safely conduct radiation research that use these radiation technologies to better the world and its people.
For more information on the radiation and its uses, please refer to www.RadiationAnswers.org